#include<iostream>
using namespace std;

int main()
{
	int p,d,m,s;
	cin>>p>>d>>m>>s;
	int cur = p;
	int count = 0;
	while(s>=cur)
	{
		count++;
		s -= cur;
		if(cur-d<m)
		{
			cur = m;
		}
		else
		{
			cur = cur-d;
		}
	}
	cout<<count;
}